Fire control system for weapons



NOV- 1966 K. G. F. LIND FIRE CONTROL SYSTEM FOR WEAPONS 2 Sheets-Sheet 1 Filed June 26, 1964 INVENTOR KARL GGRAN FOLKE LiND 'N v- 29, 1966 K. G. F. LIND 3,288,030

FIRE CONTROL SYSTEM FOR WEAPONS Filed June 26, 1964 2 Sheets-Sheet ,2

FIG.2

INVENT OR KARL G'O'RAN FOLKE LIND United States Patent Sweden Filed June 26, 1964, Ser. No. 378,250 Claims priority, application Sweden, July 1, 1963,

,2s7 13 Claims. (Cl. 89-41) The present invention is related to a fire control system, in particular to a fire control system for firing at air targets from ships.

A complete fire control system of this kind comprises sighting means for determining the direction and range to the target to be fired at, and a fire control computer, either of the analogue or the digital type, to which data are supplied from the sighting means regarding the direction and the range to the target, and which computes the trajectory and the velocity of the target from these data. On the basis of the computed trajectory and velocity of the target and additional data supplied to the fire control computer, for instance, the muzzle velocity and the ballistic properties of the projectile, the direction and the velocity of the wind, the speed, course and attitude of the ship, the parallax distance between the sight and the weapon, which is to fire at the target, etc., the computer computes the point in space, that is, the point of aim, at which the weapon is to be aimed at each moment to cause a projectile fired by the weapon to hit the target. Guided by the computed coordinates for the point of aim, the fire control computer computes further the elevation angle and the train angle, which must be applied to the weapon to direct the same at the point of aim. Signals representing the elevation angle and the train angle are transmitted from the fire control computer to servo systems for laying the weapon about its elevation axis and train axis respectively. A fire control system of this type is, however, comparatively complicated, space-consuming and expensive, whereby it cannot be used on small ships or for small, movable anti-aircraft batteries on land. Even large ships can normally be provided only with a small number of complete fire control systems of this type. As a result, a demand exists to have available for large ships also a more simple fire control system, which can be used as an emergency system, if the complete fire control system is put out of operation, or if it is desired to fire at several targets simultaneously with different weapons on the ship.

The mos-t simple fire control system consists of a detector or sight, which can be directed in elevation and in traverse at a target to be fired at and which is provided with signal generators generating signals representing the traverse angle and the elevation angle of the sight. These signals are directly fed to servo-systems for laying the weapon in accordance with the direction of the sight. ,Such servo-systems may consist of two signal comparison devices, to which the signals representing the traverse .angle and the elevation angle respectively of the sight are supplied and which determine the diiferences between the traverse angle and the elevation angle respectively of the sight and the train angle and the elevation angle respectively of the weapon. The difference signals from the comparison devices are then fed as control signals to servomotors arranged to lay the weapon about its train .axis and its elevation axis respectively, until the control signals supplied to the servomotors become zero. A fire control system of this very simple type comprises no fire control computer in the true sense and the weapon will be laid parallel with the sight. However, due to various factors, as for instance, the gravity correction, the movement of the target, the speed wind as caused by the movement of the ship, the real wind, the parallax distance between the weapon and the sight, etc., certain deflection angles between the train angle and the elevation angle respectively of the weapon and the traverse angle and the elevation angle respectively of the sight are necessary for a projectile fired by the weapon to hit the tar-get.

It is an object of the present invention to provide a simple fire control system of the type mentioned above, in which the signals representing the traverse angle and the elevation angle respectively of the sight are directly fed to servo-systems for laying the weapon in traverse and in elevation, but with which it is nevertheless possible by simple means to determine the necessary deflection angles between the traverse angle and the elevation angle respectively of the sight and the train angle and the elevation angle respectively of the weapon and to introduce the .deflection angles into the servo-systems for the laying of the weapon. According to this invention, this is achieved by a fire control system which comprises an analog computer computing, at least approximately, the deflection angles between the traverse angle and the elevation angle respectively of the sight and the train angle and the elevation angle respectively of the weapon, which are necessary with respect to, for instance, the gravity correction, the movement of the target, the speed wind caused by the movement of the ship, the real wind, any parallax present between the sight and the weapon, etc. The computer produces signals proportional to these deflection angles, which signals are fed as control signals to the servomotors laying the weapon about its train axis and its elevation axis respectively together with the control signals obtained from the signal comparison devices. For the computation of the aforementioned deflection angles between the direction of the weapon and the direction of the sight the analog computer must have access to certain trigonometric functions, primarily the sine and cosine functions of the traverse angle and the elevation angle of the sight and therefore the fire control system .acording to the invention further comprises signal generators, which are mechanically coupled to the sight. These generators generate and convey to the analog computer signals proportional to those trigonometric functions of thetraverse angle between the direction of the sight and a fixed direction in the site of the sight, preferably the fore and aft direction of -the ship, and of the elevation angle between the direction of the sight and a fixed plane in the site of the sight, preferably the deck plane of the. ship, said signals being necessary for the computation in the analog computer of the deflection angles between the direction of the sight and the direction of the weapon.

The signal generators may, for instance, comprise separate sine and cosine potentiometers, which are mechanically coupled to the sight in sucha way that they are rotated in accordance with the directing of the sight in traverse and elevation respectively. In a particularly advantageous embodiment of the invention, the samesigna-l generators, mechanically coupled to the sight, may 'be used for producing the signals directly fed to the servo-systems of the weapon and representing the traverse angle and the elevation angle respectively of the sight and also for producing the signals connected to the analog computer and proportional to the sine and cosine functions of the traverse angle and the elevation angle respectively of the sight. This is achieved according to the invention by providing in the fire control system a first electrical transmitter resolver of conventional kind, the two mutually rotatable partsof which are provided with a primary winding fed from a constant alternating voltage and two mutually orthogonally oriented secondary windings respectively. The .rotor of the resolver is mechanically coupled to the sight in such a way that it is rotated relative to the stator in accordance with the directing of the sight in traverse. The two secondary windings of the resolver are connected to each one of the two mutually orthogonally oriented primary windings on the one of the two mutually rotatable parts of a first electrical comparison resolver of conventional kind. The second part of this resolver is provided with a secondary winding and the rotor is mechanically coupled to the weapon in such a way that it is rotated relative to the stator of the comparison resolver in accordance with the training of the weapon. The voltage induced in the secondary winding of the comparison resolver is fed as a control voltage to the servomotor laying the weapon about its train axis. The fire control system also comprises a second similar conventional transmitter resolver, the rotor of which is mechanically coupled to the sight in such a way that it is rotated relative to the stator of said resolver in accordance with the elevation of the sight. The two secondary windings of the second transmitter resolver are connected to the two primary windings of a similar second electric comparison resolver, the rotor of which is mechanically coupled to the weapon in such a way that it is rotated relative to the stator in accordance with the elevation of the weapon. The secondary voltage of the second comparison resolver is fed as a control voltage to the servomotor laying the weapon about its elevation axis. The rotors of the transmitter resolvers can then be given a datum position relative to the stators of the resolver such that the voltages obtained from the secondary windings of the first transmitter resolver are proportional to sin and cos 0', respectively, where o' is the traverse angle between the direction of the sight and a predetermined fixed direction in the site of the sight, preferably the fore and aft direction of the ship. The voltages obtained from the secondary windings of the second transmitter resolver are proportional to sin x and cos where X is the elevation angle between the direction of the sight and a predetermined fixed plane in the site of the sight, preferably the deck plane of the ship. Consequently, the voltages obtained from the secondary windings of the transmitter resolver-s are proportional to the sine and the cosine functions of the traverse angle and the elevation angle of the sight and these voltages may be fed to the analog computer as input data for the computation in the analog computer of the deflection angles between the direction of the weapon and the direction of the sight.

Instead of transmitter resolvers and comparison resolvers one can according to the invention also use conventional transmitter synchros and comparison synchros, which are distinguished from the resolvers in that the one of the two mutually rotatable parts of a synchro is provided with three windings, oriented at 120 to each other, instead of two mutually orthogonally oriented windings. The voltages received from the three secondary windings of the two transmitter synchros, which are mechanically coupled to the sight, will not be proportional to the sine and cosine functions of the traverse angle and the elevation angle respectively of the sight, but proportional voltages may be obtained comparatively easily by means of two transformers coupled for converting-a three-phase system to a two-phase system, for instance, Scott-transformers, which have their three-phase terminals connected to one each of the two transmitter synchros. The voltages obtained from the two-phase terminals of the transformers will then be proportional to sin a and cos a and respectively sin X and cos provided that the rotors of the transmitter synchros have a correct datum position relative to the stators of the synchros.

In the following, the invention will be further described with reference to the accompanying drawing, in which:

FIG. 1 shows schematically, by way of example, one embodiment of a fire control system according to the invention for firing at air targets from a ship, and

FIG. 2 shows a detail of a modification of the system shown in FIG. 1. v

The -fire control system shown in FIG. 1 comprises a detector or sight S, which is schematically shown as an optical sight, but which may be of any suitable type, for instance, :a radar sight. As schematically shown, the sight S may be directed in traverse and in elevation at a target M, which is to be fired at. The directing in traverse is carried out by means of a servomotor S1, which is arranged to turn the platform -1, on which the sight is mounted, about an axis perpendicular to the deckplane of the ship. The directing in elevation of the sight S is carried out by means of a servomotor S2, which pivotes the sight S in a stand -2 about an axis parallel with the deck-plane of the ship. The traverse angle 0' of the sight is defined as the angle on the deck-plane of the ship between the direction of the sight and the foreand-a-ft direction 0 of the ship, and the elevation angle )4 of the sight is defined as the angle between the direction of the sight and the deck-plane of the ship. An operator may direct the sight S at the target M by means of a control lever 3 which is at one end coupled to a mechanic-a1 gear device 4 in such a way that the control lever 3 can be displaced in a substantially orthogonally coordinate system, in which the one coordinate direction corresponds to directing of the sight S in traverse and the second coordinate direction corresponds to directing of the sight in elevation. The mechanical gear device 4 has two output shafts 5, 6, one of them, 5, being rotated in accordance with the displacement of the control lever 3 in the coordinate direction corresponding to the traverse directing of the sight, whereas the second shaft 6 is rotated in accordance with the displacement of the control lever 3 in the second coordinate direction corresponding to elevation directing of the sight 8. A conventional potentiometer P1 and P2 respectively fed from a constant alternating voltage is connected to each one of the out-put shafts 5 and 6. The potentiometer P1 will consequently provide a voltage, which is proportional to the deflection of the control lever 3 from its zero position in the coordinate direction corresponding to traverse directing of the sight, whereas the potentiometer P2 will provide a voltage, which is proportional to the deflection of the control lever 3 from the zero position in the coordinate direction corresponding to elevation of the sight. The voltage outputs of the potentiometers P1 and P2 are fed through amplifiers F1 and F2 respectively as control signals to the servomotors S1 and S2 respectively. The sight S is further provided with two angular velocity-sensitive gyros G1 and G2, which are mounted on the sight in such a way that they participate in the traversing and the elevation of the sight. Accordingly, the gyro G1 is aifectecl by the angular velocity of the sight about an axis which is perpendicular to the line of sight as well as the elevation axis of .the sight, and thus produces a voltage dependent of this angular velocity. This voltage is fed as a negative feed-back through the amplifier F1- to the servomotor S1. The gyro G2 senses the angular velocity of the sight about its elevation axis and produces a signal dependent hereof which is fed as a negative feed-back through the amplifier F2 to the servomotor S2. Hence, the servomotors S1 and S2 are controlled by the differences, highly amplified in the amplifiers F1 and F2, between the signals from the potentiometer P1 and the gyro G1 and from the potentiometer P2 and the gyro G2 respectively. In this way the direction of the sight S is maintained stabilized in space independent of the movements of the ship, without the operator having to operate the control lever 3. It is evident that when the operator follows by means of the control 3 the target M with the sight S, the voltage from the potentiometer P2 is proportional to the angular velocity d M/dz of the target M in space relative to the elevation axis of the sight, and the voltage from the potentiometer P1 is proportional to the angular velocity of the target 'M in space about the axis which is perpendicular to the elevation axis of the sight as well as to the line of sight, that is, proportional to daM/dt cos where daM/dt is the angular velocity of the target in space about the traversing axis of the sight, which axis is perpendicular to the deck-plane of the ship.

The weapon V, which is to be laid at the point of aim R by means of the sight S and the fire control system, may be trained by means of .a servomotor S3 which turns a platform 7 mounting the weapon about an axis perpendicular to the deckaplane of the ship. The weapon is elevated by means of a servomotor S4 which turns the weapon V in .a stand 8 mounted on the platform 7 about an elevation axis parallel with the deck plane. The train tangle of the weapon 0 is the angle in the deckplane between the direction of the weapon and the foreand-alft direction 0 of the ship, whereas the elevation angle Xv of the weapon is the angle between the direction of the weapon and the deck-plane of the ship. One has that o' =o'+Ao', where Air is the traverse deflection angle between the direction of the weapon and the direction of the sight, which is necessary in view of, for instance, the parallax distance between the weapon and the sight, the movement of the target, the speed wind caused by the movement of the ship, etc. Furthermore, one has that +A where A is the elevation deflection angle between the direction of the weapon and the direction of the sight, which is necessary in view of, for instance, the gravity correction, the parallax distance between the weapon and the sight, the movement of the target, the speed wind caused by the movement of the ship, etc. The laying of the weapon in traverse is controlled from the sight by means of an electric transmitter resolver R1 of conventional type. The rotor of the resolver is mechanically coupled to the traversing system of the sight S in such a way that it is rotated relative to the stator of the resolver in accordance with the traversing of the sight. The rotor of the resolver is as normal provided with a primary winding 10 ted from a constant alternating voltage, whereas the stator of the resolver is provided with two mutually orthogonally oriented secondary windings 11 and 12. The rotor of the resolver R-l has further such a basic orientation relative to the stator that the direction of the field of the primary winding is parallel with the direction of the field of the one secondary winding, when the sight is so directed that o' is zero, whereby the voltage from the one secondary winding will be proportional to sin a and the voltage from the secondary winding will be proportional to cos a. The two secondary windings 11 and 12 of the resolver R1 are connected directly to the two mutually orthogonally oriented primary windings 13 and 14 on the stator of an electric comparison resolver R2 of conventional type. The rotor of the resolver R2 is mechanically coupled to the traverse laying system of the weapon V in suchwa way that it is rotated relative to the stator of the resolver R2 in accordance with the direction of the weapon V in traverse relative to the fore-and-aft direction of the ship. In the secondary winding 15 on the rotor of the resolver R2 a voltage is consequently induced, which is proportional to sin (u' -o'). This voltage is fed through an amplifier F 3 as a control voltage to a servomotor S3 laying the weapon in traverse. The servomotor S3 tends to turn the weapon in traverse until the supplied control signal becomes zero, that is, until o' =zr, provided that no additional control} voltage is connected to the servomotor S3 through the amplifier P3. In the embodiment shown, the two mutually orthogonally oriented windings of the resolvers R1 and R2 are mounted on the stators of the resolvers, but as well known, they may instead be mounted on the rotors of the resolvers, while the primary winding of the transmitter resolver R1 is mounted on the stator of the transmitter resolver and the secondary winding of the comparison resolver R2 is mounted on the stator of the comparison resolver.

The laying of the weapon in elevation is controlled by the sight S in a corresponding manner, by means of an electric transmitter resolver R3, which has the same design as the transmitter resolver R1 .and therefore is shown only schematically. The rotor of the transmitter resolver R3 is mechanically coupled to the elevation system of the sight S in such a way that it is. rotated relative to the stator of the resolver R3 in accordance with the elevation of the sight. The basic orientation of the rotor relative to the stator is such that the voltage from the one secondary winding ol? the transmitter resolver -R3 is proportional to sin whereas the voltage from the second secondary winding of the transmitter resolver R3 is proportional to cos The secondary windings of the transmitter resolver R3 are directly connected to the mutually orthogonally oriented primary windings on the stator of a conventional electrical comparison resolver R4 of the same design as the comparison resolver R2. The rotor of the comparison resolver R4 is mechanically coupled to the elevating system of the weapon V in such a way that it is rotated relative to the stator of the comparison resolver R4 in accordancewith the elevation of the weapon relative to the deckpl-ane of the ship. The voltage induced in the secondary winding of the comparison resolver R4 is consequently proportional to sin (x x and is connected through .an amplifier F4 as a control voltage to a servomotor S4, which is laying the weapon V in elevation. The servomotor S4 tends to lay the weapon in elevation, until the supplied control signal becomes zero, that is, until provided that no additional control voltage is supplied to the servomotor S4 through the amplifier F4.

As mentioned above, a certain deviation A0 is however uecessary between the traverse direction 0., of the weapon and the traverse direction 0' of the sight. For this purpose the amplifier B3 is supplied, in addition to the voltage proportional to sin =(o' -0') from the comparison resolver R2, also with a second voltage proportional to A0 from an analogue computer to be, described later on. The two control voltages are connected to the amplifier F3 in such a way that they oppose one another. As a result, the servomotor R3 is controlled by the IdilTerence between the two controlvoltages and thus lay the weapon V in traverse until sin -(a' a')=Ao'. As (TV-0' is a very small angle it is approximately true that the servomotor S3 will lay the weapon V in traverse, until 0' 0'=AtT, that is, until the desired traverse direction o' of the weapon is reached. Similarly, a certain deflection angle A is necessary between the elevation Xv of the weapon V and the elevation x of the sight S. for this purpose the amplifier F4 is supplied, in addi tion to the voltage proportional to sin (x -x) from the comparison resolver R4, with a voltage proportional to A from the analogue computer. In this case also the two signals are supplied to the amplifier F4 in such a way that they are opposing one another, whereby the servomotor S4 is controlled by the difference between the signal proportional tosin and the signal proportional to A and thus lay the weapon V in elevation until it is approximately true that x x=Aq-, that is, until the desired elevation angle Xv is imparted to the weapon.

The analogue computer for computing the signal voltalges proportional to A0 and A comprises in the exam-plified embodiment of the invention tour potentiometers P3, P4, P5 and P6 which may be set, in accordance with the slant range L to the target M, tor instance, manually or automatically from a range measuring device, for instance, a radar station or. an optical range measuring instrument. The potentiometers P3 and P5 have a directly proportional resistance characteristic and their output voltages are consequently directly proportional to the range L to the target whereas the potentiometers P4 and P6 have inversely proportional resistance characteris'tics so that their output voltages are proportional to l/L. The potentiometers P4 and P6 may, however, also have proportional resistance characteristics and be provided with a fixed output and a division coupling. The division function l/L can the achieved also in other ways, for instance, 'by means of an amplifier with a variable feed-back. The analogue computer {further comprises two potentiometers P7 and 'P8 Which can be set in accordance with the speed of the ship, that is, in accordance with the speed wind F caused by the movement of the ship, either manually in discrete steps, or automatically and continuously from the speed log of the ship. In addition, the analogue computer comprises two potentiometers P9 and P10, which are mechanically coupled to the elevation system of the sight S and have resistance characteristics such that the output voltage of the potentiometer P9 is proportional to 1/ cos X and the output voltage from the potentiometer P10 is proportional to Finally, the analogue computer comprises a number of amplifiers F5 to F10 for introducing necessary proportionality factors, the values of which are dependent on inter alia the parallax distance between the weapon V and the sight S and the projectile velocity of the weapon V.

In the described embodiment of the invention the necessary traverse deflection angle Ac between the traverse angle 0., of the weapon and the traverse angle of the sight comprises a component Aa caused by the parallax distance between the weapon V and the sight S, a component AO'F caused by the speed wind F due to the move ment of the ship, and a component Ao' caused by the movement of the target M. The elevation deflection angle A between the elevation angle Xv of the weapon V and the elevation angle X of the sight S comprises correspondingly a component A caused by the parallax distance between the weapon and the sight, a component A caused by the speed wind, a component A caused by the movement of the target M, and a component A corresponding to the necessary gravity correction.

As an approximation for the traverse deflection angle Aa as caused by the parallax, one uses according to the invention a voltage proportional to sin a/L which is produced in the analogue computer by supplying to the adder amplifier F6 a voltage from the potentiometer P6 which is fed through the amplifier F10 with a voltage proportional to sin 0' from the secondary winding 13 of the transmitter resolver R1. This approximation is reached according to the invention in the following way. In view of the small magnitude of the parallax and the over all accuracy of the system, one can be satisfied with the first term in a Taylor series, whereby one obtains:

- Sine" 1/ cos X0, where X0 is a typical elevation angle. Normally X has a rather limited range of variation. This gives 7 AU K1.Sin tT/L in which the coefiicient K comprises all coefiicients in the expression (1).

As an approximation for the traverse deflection angle Ao' as caused by the speed wind, one uses, according to the invention, a voltage proportional to LF sin a, which is produced in the analogue computer by supplying to the adder amplifier F6 a voltage component from the potentiometer P which is fed with the voltage from the adder amplifier F9, which in turn is fed through the amplifier F10 with the voltage proportional to sin 0' from the secondary winding 11 of the transmitter resolver R1. The following reasoning gives this approximation.

The traverse deflection angle due to the speed wind is determined with good accuracy (according to outer ballistics) by the following expression:

0 V l cos X (3) Where c is a measure of the retardation properties of the projectile, V is the muzzle velocity of the projectile, V its average velocity, A the distance to the point of hit and F the force of the wind.

In view of the magnitude of the deflection angle and the over-all errors of the system, the following approximation may be used.

the coefficients are combined to a single coefficient one obtains:

As an approximation for the traverse deflection angle Ac as caused by the movement of the target, one uses according to the invention a voltage proportional to daM that is, a voltage proportional to the product of the slant range L to the target M and the angular velocity of the target in space about the traverse directing axis of the sight. For this approximation one assumes that the projectile velocity of the weapon is constant and consequently that the time of flight of the projectile is directly proportional to the slant range L to the target. This voltage is produced in the analogue computer by feeding the amplifier P6 with an additional voltage component from the potentiometer P5 by supplying to the adder amplifier F9, which is feeding the potentiometer PS, the voltage from the potentiometer P9 which is fed with the voltage proportional to daM/a't cos X from the potentiometer P1. This approximation may be deduced in the following way. For the traverse movement of the target one makes the approximation that the traverse angular velocity of the target daM/dt is assumed to be constant during the time of flight of the projectile, which is a good approximation, when the target trajectory is close to straight towards the sight, for typical ranges and with typical crossing point distances. This approximation gives:

assumed to be constant. This gives daM A (Tt K dt L (7) As an approximation for the elevation deflection angle A due to the parallax, one uses according to the invention a voltage proportional to (cos -k cos 1) /L, where k is a factor of proportionality dependent on the parallax between the weapon and the sight. This voltage is produced in the analogue computer by supplying to the adder amplifier F5 the voltage from the potentiom eter P4- Which, in turn, is fed from the adder amplifier F8. This voltage is supplied by the voltage proportional to cos X from the one secondary winding of the transmitter resolver R3 and by the voltage from the potentiometer 9 P10 which is fed from the voltage proportional to cos a from the secondary winding 12 of the transmitter resolver Rl. This approximation may be deduced, just as the approximation for the traverse angle parallax, by using only the first term in a Taylor series, which yields:

V...+ b V..+F

L Vm -eos x As an approximation for the elevation deflection angle A due to the speed wind, one uses according to the invention a voltage proportional to LF cos which is produced by the analogue computer in that the adder amplifier F is supplied with a voltage component from the potentiometer P3, which is fed from the adder amplifier F7. This amplifier is supplied a voltage from the potentiometer P8, which is fed through the potentiometer P with the voltage proportional to cos a from the secondary winding 12 of the transmitter resolver R1. This approximation is arrived at due to the fact that the elevation deflection angle due to the speed wind is determined with good accuracy (according to the external ballistics) by the expression:

C A .A .F. cos 0'. sin X in which the symbols have the same significance as before. With the earlier approximation sin one obtains A =K -F-L- C080 (11) where K; comprises all the coeflicients.

As an approximation for the elevation deflection angle A caused by the movement of the target one uses according to the invention a voltage proportional to that is, a voltage proportional to the product of the slant range L to the target M and the angular velocity of the target in the space about the elevation axis of the sight. For this approximation it is again assumed that the projectile velocity of the weapon is constant and thus that the time of flight of the projectile is directly proportional to the slant range L to the target. This approximation may be deduced by the same reasoning as the one used with respect to the movement of the target in traverse. This voltage is produced in the analogue computer in that the adder amplifier F5 is supplied from the potentiometer P3 with an additional voltage component by supplying the adder amplifier F7 with the voltage proportional to d M/dt from the potentiometer P2.

As an approximation for the elevation deflection angle A which corresponds to the necessary gravity correction, one uses according to the invention a voltage proportional to L cos which is produced by the analogue computer in that the adder amplifier F5 is supplied from the potentiometer P3 with a third voltage component Which is obtained by supplying the adder amplifier P7 with the voltage proportional to cos x from the respective secondary winding of the transmitter reslover R3. This approximation for the gravity correction is arrived at in the following way. During the time of flight Ts of the 10 projectile, the same will fall the distance d in perpendicular direction.

2 d 2 (Ts) where g is somewhat smaller than the ground acceleration due to the lift eifect (compare the outer ballistics). This gives the gravity correction angle:

2 1 l Ax 2 (Ts) cos with all the coeflicients combined to one coefflcient, beamended to @142 COS X which, with the approximation A =LV (V +F and with all the coeificients combined as one coefiicient, becomes:

A =K 'L' COS X (14) It is obvious that in the chains of cascade-connnected potentiometers in the analogue computer it does not matter in principle, in which order the potentiometers are connected to one another, but with the connection shown in FIG. 1 it is possible to reduce the number of potentiometers in the computer to a minimum.

Furthermore, it is obvious that in a fire control system according to the invention, the analogue computer may be arranged to compute additional components of deflection angle between the direction of the weapon and the direction of the sight, as for instance, those which are necessary due to the real wind. For the computation of the deflection angles caused by the real wind, the wind is preferably split into two components, one directed in the fore-and-aft direction of the ship and thus parallel with the speed Wind, which component may be treated in the analogue computer together with the speed wind component, whereas the other component of the real Wind is at right angle to the fore-and-aft direction of the ship and consequently requires a separate computation in the analogue computer. Other deflection angle components may, of course, also be computed by the analogue computer, if necessary. Furthermore, the analogue computer may be arranged to use approximations for the various deflection angle components other than those mentioned above. It is, however, advantageous to use approximations, which comprise substantially only sine and cosine functions of the traverse angle and the elevation angle respectively of the sight, as voltages proportional to these functions are directly available from the secondary windings of the two transmitter resolvers R1 and R3.

As already mentioned, one can also produce the voltages proportional to the sine and cosine functions of a and which are necessary for the analogue computer, by means of sine and cosine potentiometers coupled to the traverse directing system and the elevation directing system respectively of the sight. This involves, however, an obvious complication of the fire control system, as it will comprise these additional potentiometers and also those mechanical elements, which are necessary for setting these potentiometers in a correct way -by means of the sight.

Instead of using transmitter resolvers and comparison resolvers for transmitting the traverse angle and the elevation angle of the sight to the servo-systems of the weapon, as in the form of the invention shown in FIG. 1 and described above, one may also use, in a fire control system according to the invention, transmitter synchros and comparison synchros for this purpose. Such a synchro transmission is shown in principle in FIG. 2. The transmitter synchro E1, which consequently is replacing, for instance, the transmitter resolver R1 in FIG. 1, is just as the transmitter resolver provided with a rotor with a primary winding 20 -fed from a constant alternating voltage. The rotor is mechanically coupled to the traverse directing system of the sight in such a way that it is rotated relative to the stator of the synchro E1 in accordance with the traverse directing of the sight. The stator of the synchro E1 is, however, in contrast to the stator of the transmitter resolver, provided with three secondary windings 21, 22 and 23 oriented at 120 from each other. These secondary windings are directly connected to the three, 120 from one another spaced windings 24, 25 and 26 on the stator of a comparison synchro E2 of the corresponding design, which is consequently replacing the comparison resolver R2. The rotor of the comparison synchro E2 is mechanically coupled to the traverse laying system of the weapon V in such a way that it is rotated relative to the stator of the synchro E2 in accordance with the traverse laying of the weapon. The rotor of the comparison synchro E2 is provided with a secondary winding 27, the voltage of which is connected as a control voltage to the servomotor S3 laying the weapon in traverse. It is appreciated that in a synchro transmission of this type the voltages obtained from the three secondary windings of the transmitter synchro E1 cannot be proportional to the sine and cosine functions of the travverse angle of the sight. Such voltages can, however, be obtained comparatively easily from the three secondary voltages of the transmitter synchro E1 by means of a transformer coupled for converting a three-phase system to a two-phase system, for instance, a Scott-coupled transformer T1, as shown in FIG. 2. This transformer has its three-phase terminals connected to the secondary voltages of the transmitter synchro E1. If the rotor of the transmitter synchro E1 is oriented in a correct way relative to the stator of the synchro, the voltage obtained from one of the two-phase terminals of the Scott-coupled transformer T1 will be proportional to sin 0, whereas the voltage from the second two-phase terminal of the transformer T1 will be proportional to cos 0. These voltages can consequently be used in the analogue computer for the computation of the deflection angles between the direction of the Weapon and the direction of the sight. This form of the invention is, however, obviously somewhat more complicated than the embodiment with resolver transmissions as shown in FIG. 1.

In addition to the traverse angle transmission and the elevation angle transmission from the sight S to the weapon V by means of the resolvers R1 and R2 and R3 and R4 respectively, as shown in FIG. 1, one normally has also an additional transmission of the traverse angle and the elevation angle of the sight for a fine laying of the weapon V. This fine laying of the weapon V is achieved by connecting two additional transmitter resolvers to the traverse directing system and the elevation directing system respectively of the sight in such a way that the rotors of these additional transmitter re solvers are rotated through the angle mr and n respectively relative to the stators of the resolvers, where n is a whole number larger than 1, for instance, 9. The sec- "ondary windings on these additional fine laying resolvers are directly connected to the primary windings on corresponding additional comparison resolvers, the rotors of which are mechanically coupled to the traverse laying system and the elevation laying system respectively of the weapon in such a way that they are rotated through the angle no and n respectively relative the stators of the comparison resolvers. The secondary voltages from these additional comparison resolvers will consequently be proportional to sin (lw na) and sin (n -n respectively and are fed to the associated servomotors S3 and S4 respectively through amplifiers and switching means which feed these fine laying signals to the servomotors when the coarse laying signals from the comparison resolvers R2 and R4 fall below a certain predetermined value. In such a system with a coarse laying system and also a fine laying system the signals proportional to A0 and A respectively received from the analogue computer are preferably fed to the servomotors S3 and S4 together with the fine laying signals. The voltages proportional to the sine and cosine functions of the traverse angle 0' and the elevation angle X of the sight supplied to the analogue computer must however be taken from the coarse laying system just as before. Such a system with a coarse laying as well as a fine laying of the weapon from the sight can, of course, also be realized by means of synchro transmissions of the type shown in FIG. 2.

Resolvers and synchros suitable -for use in a fire control system according to the invention are described, for instance, in the textbook Electromagnetic Components for Servomechanisms by Sidney A. Davis and Byron K. Ledgerwood, published by McGraw-Hill, New York, 1962.

What is claimed is:

1. A fire control system for aiming a weapon movable in traverse and elevation at a remote target comprising: a first servomotor means including a traverse control signal input and a mechanical output coupled to said weapon for moving the latter to a different traverse angle when a control signal is received at said traverse control signal input; a second servomotor means including an elevation control signal input and a mechanical output coupled to said weapon for moving the latter to a different elevation angle when a control signal is received at said elevation control signal input; a sight directable to different traverse angles and different elevation angles; a first transmitting resolver comprising a rotor part and a stator part, a primary winding on one of said parts, means for feeding a constant peak amplitude A.C. voltage to said primary winding, two mutually orthogonally oriented secondary windings on the other of said parts, means for coupling said rotor part to said sight whereby one of said secondary windings transmits a voltage proportional to sin a and the other of said secondary windings transmits a voltage proportional to cos 0-, 0' being the traverse angle of said sight with respect to a given direction; a second transmitting resolver comprising a rotor part and a stator part, a primary winding on one of said parts, means for feeding a constant peak amplitude A.C. voltage to said primary winding, two mutually orthogonally oriented secondary windings on the other of said parts, means for coupling said rotor part to said sight whereby one of said secondary windings transmits a voltage proportional to sin X and the other of said windings transmits a voltage proportional to cos X being the elevation angle of said sight with respect to a given plane; a first comparison resolver comprising a stator part and a rotor part, two mutually orthogonally oriented primary windings on one of said parts, a secondary winding on the other of said parts, means for connecting said rotor part to the mechanical output of said first servomotor means, means for connecting one of said secondary windings of said first transmitting resolver to one of the primary windings of said first comparison resolver, means for connecting the other of said secondary windings of said first transmitting resolver to the other of the primary windings of said first comparison resolver whereby the secondary winding of said first comparison resolver transmits a voltage proportional to sin (a a), o' being the traverse angle of said weapon with respect to said given direction, said voltage constituting a primary traverse control signal; a second comparison resolver comprising a stator part and a rotor part, two mutually orthogonally oriented primary windings on one of said parts, a secondary winding on the other of said parts, means for connecting said rotor part to the mechanical output of said second servomotor means, means for connecting one of the secondary windings of said second transmitting resolver to one of the primary windings of said second comparison resolver, means for connecting the other secondary winding of said second transmitting resolver to the other primary winding of said second comparison resolver whereby the secondary Winding of said second comparison resolver transmits a voltage proportional to sin Xv being the elevation angle of said weapon with respect to said given plane, said voltage constituting a primary elevation control signal; computer means including signal inputs connected to at least one of the secondary windings of said first transmitting resolver and at least one of the secondary windings of said second transmitting resolver, a first signal output for transmitting a deflection traverse control signal which is trigonometrically related to the traverse angle of said sight and a second signal output for transmitting a deflection elevation control signal which is trigonometrically related to the elevation angle of said sight;-means for feeding the sum of said primary and deflection traverse control signals to the traverse control signal input of said first servomotor means; and means for feeding the sum of said primary and deflection elevation control signals to the elevation control signal input of said second servomotor means. I

2. The system of claim 1 further comprising control means for said sight, said control means being displaceable in first and second orthogonal directions respectively related to the traverse and elevation directions of said sight, a first voltage generator mechanically coupled to said control means for generating a voltage proportional to the deviation of said control means in said first orthogonal direction from a given zero position, a second voltage generator mechanically coupled to said control means for generating a voltage proportional to the deviation of said control means in said second orthogonal direction from a given zero position, a third servomotor means including a mechanical output coupled to said sight for moving the latter in traverse directions and a voltage input connected to said first voltage generator, a fourth servomotor means including a mechanical output coupled to said sight for moving the latter in elevation directions, a first angular-velocity-sensitive gyro signal generator mounted on said sight for generating a first angular velocity signal related to the angular velocity of said sight about an axis perpendicular to the direction of said sight and an elevation axis of said sight, said first gyro signal generator including a negative feedback output connected to the voltageinput of said third servomotor means, a second angular-velocity-sensitive gyro signal generator mounted on said sight for generating a second angular velocity signal related to the angular velocity of said sight about said elevation axis, said second gyro signal generator including a negative feedback output connected to the voltage input of said fourth servomotor means, and where-in said computer comprises a first potentiometer including a resistanceelement having a directly proportional resistance characteristic and a first slider adjustable in accordance with L, L being; the distance from said sight to the target, means for connecting said first resistance element to said first voltage generator so that said first slider transmits a voltage proportional to L where is the elevation velocity of the target, means for connecting said first slider to the second signal output of said computer, a second potentiometer including a second resistance element having a directly proportional resistance characteristic adjustable in accordance with L and a second slider, a third potentiometer including a third resistance element having; an inversely proportional cosine characteristic and a third slider mechanically connected to said sight so that said third slider is adjustable in accordance with X being the angle between the direction of said sight and said given plane, means for connecting said third resistance element to said first voltage generator so that said third slider transmits a voltage proportional to cos x, where u' is the traverse velocity of the target, and means for connecting said third slider to said second resistance element so that said second slider transmits a voltage proportional to Lo cos x, and means for connecting said second slider to the first signal output of said computer.

3. The system of claim 1 wherein said computer transmits a deflection elevation control signal proportional to L cos x, L being the distance from said sight to the target, as an approximation to a gravity correction, said computer including a potentiometer having a resistance element with a directly proportional resistance characteristic and a slider adapted to be adjusted in accordance with the distance L, means for connecting said resistance element to one of the secondary windings of said second transmitting resolver whereby a voltage proportional to cos X is transmitted to said potentiometer, and means for connecting said slider to the second signal output of said computer whereby said second signal output transmits said deflection elevation control signal proportional to L cos X to said second summing means.

4. The system of claim 1 wherein said computer comprises: a first potentiometer including a first resistance element having a directly proportional resistance characteristic and a first slider adjustable in accordance with L, L being the distance from said sight to the target; a second potentiometer including a second resistance element having a directly proportional characteristic and a second slider adjustable in accordance with F, F being the speed wind; means for connecting said second resistance element to one of the secondary windings of said first transmitting resolver so that said second slider transmits a voltage proportional to F sin; means for connecting said second slider to said first resistance element so that said first slider transmits a voltage proportional to FL sin a; and means for connecting said first slider to the first signal output of said computer.

5. The system of claim 1 wherein said computer comprises: a first potentiometer including a first resistance element having a directly proportional resistance characteristic and a first slider adjustable in accordance with L, L being the distance from said sight to the target: a second potentiometer including a second resistance element having a directly proportional resistance characteristic and a second slider adjustable in accordance with F, F being the speed wind; a third potentiometer including a third resistance element having a directly proportional characteristic and a third slider adjustable in accordance with x; means for connecting said third resistance element to one of the secondary windings of said first transmitting resolver so that said third slider transmits a voltage proportional to x cos 0'; means for connecting said second resistance element to said third slider so that said second slider transmits a voltage proportonal to F- cos a; means for connecting said second slider to said first resistance element so that said first slider transmits a voltage proportional to F -L cos 0'; and means for connecting said first slider to the second signal output of said computer.

6. The system according to claim 1 wherein said computer comprises: a potentiometer including a resistance element having aninversely proportional resistance characteristic and a slider adjustable in accordance with L, L being the distance from said sight to the target; means for connecting said resistance element to one of the secondary windings of said first transmitting resolver so that said slider transmits a voltage proportional to l/L Si1'I;o'; and means for connecting said slider to the first signal output of said computer.

7. The system according to claim 1 wherein said computer comprises: a first potentiometer including a first resistance element having an inversely proportional resistance characteristic and a slider adjustable in accordance with L, L being the distance from said sight to the target; an intermediate summing means for adding two voltages including a sum output and first and second operand inputs; a second potentiometer including a second resistance element having a directly proportional resistance characteristic and a second slider adjustable in accordance with means for connecting said first operand input to one of the secondary windings of said second transmitting resolver so that a voltage proportional to cos X is fed to said intermediate summing means; means for connecting said second resistance element to one of the secondary windings of said first transmitting resolver so that a voltage proportional to kcos is transmitted from said second slider; means for connecting said second slider to said second operand input; means for connecting said first resistance element to said sum output so that first slider transmits a voltage proportional to (cos +kcos o')/L; and means for connecting said first slider to said second signal output of said computer.

8. A fire control system for aiming a weapon movable in traverse and elevation at a remote target, comprising: a first servomotor means including atraverse control signal input and a mechanical output coupled to said weapon for moving the latter to a different traverse angle when a control signal is received at said traverse control signal input; a second servomotor means including an elevation control signal input and a mechanical output coupled to said weapon for moving the latter to a different elevation angle when a control signal is received at said elevation control signal input; a sight directable to different traverse angles and different elevation angles; a first transmitting synchro comprising a rotor part and a stator part, a primary winding on one of said parts, means for feeding a constant peak A.C. voltage to said primary winding, three equiangularly displaced secondary windings on the other of said parts, means for connecting said rotor to said sight; a first comparison synchro comprising a rotor part and a stator part, three equiangularly displaced primary windings on one of said parts, a secondary winding on the other of said parts, means for connecting said rotor to the mechanical output of said first servomotor means; means for respectively connecting each of secondary windings of said first transmitting synchro to a different one of the primary windings of said first comparison synchro, said secondary winding transmitting a primary traverse control signal; a second transmitting synchro comprising a rotor part and a stator part, a primary winding on one of said parts, three equiangularly displaced secondary windings on the other of said parts, means for feeding a constant peak AC. voltage to said primary winding, means for connecting said rotor to said sight; a second comparison synchro comprising a rotor part and a stator part, three equiangularly displaced primary windings on one of said parts, a secondary winding on the other of said parts for transmitting a primary elevation control signal and means for connecting the rotor to the mechanical out put of said second servomotor means; means for respectively connecting each of the secondary windings of said second transmitting synchro to a different one of the primary windings of said second comparison synchro respectively; said system further comprising first and second transformer means for converting a three-phase system to a two-phase system, each of said transformer means comprising three Y-connected primary windings and two secondary windings, means for respectively connecting each of the primary windings of said first transformer means to a different one of the secondary windings of said first transmitting synchro whereby the secondary windings of said first transformer means transmit respectively voltages proportional to sin 0' and cos a, where 0' is the traverse angle of said sight with respect to a given direction; means for respectively connecting each of the secondary windings of said second transmitting synchro to a different one of the primary windings of said second transformer means whereby the secondary windings of said second transformer means respectively transmit voltages proportional to sin X and cos where X is the elevation angle of said sight with respect to a given plane, computer means including signal inputs connected to at least one of the secondary windings of said first transformer means and to at least one of the secondary windings of said second transformer means, a first signal output for transmitting a deflection traverse control signal which is trigonometrically related to the traverse angle of said sight and a second signal output for transmitting a deflection elevation control signal which is trigonometrically related to 1% the elevation angle of said sight; means for feeding the sum of said primary and deflection traverse control signals to the traverse signal input of said first servomotor means; and means for feeding the sum of said primary and deflection elevation control signals to the elevation signal input of said second servomotor means.

9. The system of claim 8 wherein said computer transmits a deflection elevation control signal proportional to L cos L being the distance from said sight to the target, as an approximation to a gravity correction, said computer including a potentiometer having a resistance element with a directly proportional resistance characteristic and a slider adapted to be adjusted in accordance with the distance L, means for connecting said resistance element to one of the secondary windings of said second transformer means whereby a voltage proportional to cos X is transmitted to said potentiometer, and means for connecting said slider to the second signal output of said computer whereby said second signal output transmits said deflection elevation control signal proportional to L cos X to said second summing means.

10. The system of claim 8 wherein said computer comprises: a first potentiometer including a first resistance element having a directly proportional resistance characteristic and a first slider adjustable in accordance with L, L being the distance from said sight to the target; a second potentiometer including a second resistance element having a directly proportional characteristic and a second slider adjustable in accordance with F, F being the speed wind; means for connecting said second resistance element to one of the secondary windings of said first transformer means so that the said second slider transmits a voltage proportional to F sin tr; means for connecting said second slider to said first resistance element so that said first slider transmits a voltage proportional to F -L sin 0'; and means for connecting said first slider to the first signal output of said computer.

11. The system of claim 8 wherein said computer comprises: a first potentiometer including a first resistance element having a directly proportional resistance characteristic and a first slider adjustable in accordance with L, L being the distance from said sight to the target; a second potentiometer including a second resistance element having a directly proportional resistance characteristic and a second slider adjustable in accordance with F, F being the speed wind; a third potentiometer including a third resistance element having a directly proportional characteristic and a third slider adjustable in accordance with means for connecting said third resistance element to one of the secondary windings of said first transformer means so that said third slider transmits a voltage proportional to X cos 0'; means for connecting said second resistance element to said third slider so that said second slider transmits a voltage proportional to F X cos 0'; means for connecting said second slider to said first resistance element so that said first slider transmits a voltage proportional to F-L- cos 0-; and means for connecting said first slider to the second signal output of said computer.

12. The system according to claim 8 wherein said computer comprises: a potentiometer including a resistance element having an inversely proportional resistance characteristic and a slider adjustable in accordance with L, L being the distance from said sight to the target; means for connecting said resistance element to one of the secondary windings of said first transformer means so that said slider transmits a voltage proportional to 1/L sin a; and means for connecting said slider to the first signal output of said computer.

13. The system according to claim 8 wherein said computer comprises: a first potentiometer including a first resistance element having an inversely proportional resistance characteristic and a slider adjustable in accordance with L, L being the distance from said sight to the target; and intermediate summing means for adding two voltages including a sum output and first and second operand inputs; a second potentiometer including a second resistance element having 21 directly proportional resistance characteristic and a second slider adjustable in accordance with means for connecting said first operand input to one of the secondary windings of said second transformer means so that a voltage proportional to cos X is fed to said intermediate summing means; means for connecting said second resistance element to one of the secondary windings of said first transformer means so that a voltage proportional to kcos a is transmitted from said second slider; means for connecting said second slider to said second operand input; means for connecting said first resistance element to said sum output so that said first slider transmits a voltage proportional to (cos +k' X cos a) /L; and means for connecting said first slider to said second signal output of said computer.

References Cited by the Examiner UNITED STATES PATENTS 8/1955 Knowles et al 89-41 12/ 1955 White 2356l.5

BENJAMIN A. BORCHELT, Primary Examiner.

FRED C. MATTERN, JR., Examiner.

W. C. ROCH, Assistant Examiner. 

1. A FIRE CONTROL SYSTEM FOR AIMING A WEAPON MOVABLE IN TRANSVERSE AND ELEVATION AT A REMOTE TARGET COMPRISING: A FIRST SERVOMOTOR MEANS INCLUDING A TRAVERSE CONTROL SIGNAL INPUT AND A MECHANICAL OUTPUT COUPLED TO SAID WEAPON FOR MOVING THE LATTER TO A DIFFERENT TRAVERSE ANGLE WHEN A CONTROL SIGNAL IS RECEIVED AT SAID TRAVERSE CONTROL SIGNAL INPUT; A SECOND SERVOMOTOR MEANS INCLUDING AN ELEVATION CONTROL SIGNAL INPUT AND A MECHANICAL OUTPUT COUPLED TO SAID WEAPON FOR MOVING THE LATTER TO A DIFFERENT ELEVATION ANGLE WHEN A CONTROL SIGNAL IS RECEIVED AT SAID ELEVATION CONTROL SIGNAL INPUT; A SIGHT DIRECTABLE TO DIFFERENT TRAVERSE ANGLES AND DIFFERENT ELEVATION ANGLES; A FIRST TRANSMITTING RESOLVER COMPRISING A ROTOR PART AND A STATOR PART, A PRIMARY WINDING ON ONE OF SAID PARTS, MEANS FOR FEEDING A CONSTANT PEAK AMPLITUDE A.C. VOLTAGE TO SAID PRIMARY WINDING, TWO MUTUALLY ORTHOGONALLY ORIENTED SECONDARY WINDINGS ON THE OTHER OF SAID PARTS, MEANS FOR COUPLING SAID ROTOR PART TO SAID SIGHT WHEREBY ONE OF SAID SECONDARY WINDINGS TRANSMITS A VOLTAGE PROPORTIONAL TO SIN $ AND THE OTHER OF SAID SECONDARY WINDINGS TRANSMITS A VOLTAGE PROPORTIONAL TO COS $, $ BEING THE TRAVERSE ANGLE OF SAID SIGHT WITH REPECT TO A GIVEN DIRECTION; A SECOND TRANSMITTING RESOLVER COMPRISING A ROTOR PART AND A STATOR PART, A PRIMARY WINDING ON ONE OF SAID PARTS, MEANS FOR FEEDING A CONSTANT PEAK AMPLITUDE A.C. VOLTAGE TO SAID PRIMARY WINDING, TWO MUTUALLY ORTHOGONALLY ORIENTED SECONDARY WINDINGS ON THE OTHER OF SAID PARTS, MEANS FOR COUPLING SAID ROTOR PART TO SAID SIGHT WHEREBY ONE OF SAID SECONDARY WINDINGS TRANSMITS A VOLTAGE PROPORTIONAL TO SIN $ AND THE OTHER OF SAID WINDINGS TRANSMITS A VOLTAGE PROPORTIONAL TO COS X, X BEING THE ELEVATION ANGLE OF SAID SIGHT WITH RESPECT TO A GIVEN PLANE; A FIRST COMPARISON RESOLVER COMPRISING A STATOR PART AND A ROTOR PART, TWO MUTUALLY ORTHOGONALLY ORIENTED PRIMARY WINDINGS ON ONE OF SAID PARTS, A SECONDARY WINDING ON THE OTHER OF SAID PARTS, MEANS FOR CONNECTING SAID ROTOR PART TO THE MECHANICAL OUTPUT OF SAID FIRST SERVOMOTOR MEANS, MEANS FOR CONNECTING ONE OF SAID SECONDARY WINDINGS OF SAID FIRST TRANSMITTING RESOLVER TO ONE OF THE PRIMARY WINDINGS OF SAID FIRST COMPARISON RESOLVER, MEANS FOR CONNECTING THE OTHR OF SAID SECONDARY WINDINGS OF SAID FIRST TRANSMITTING RESOLVER TO THE OTHER OF THE PRIMARY WINDINGS OF SAID FIRST COMPARISON RESOLVER WHEREBY THE SECONDARY WINDING OF SAID FIRST COMPARISON RESOLVER TRANSMITS A VOLTAGE PROPORTIONAL TO SIN ($V-$), $V BEING THE TRAVERSE ANGLE OF SAID WEAPON WITH RESPECT TO SAID GIVEN DIRECTION, SAID VOLTAGE CONSTITUTING A PRIMARY TRAVERSE CONTROL SIGNAL; A SECOND COMPARISON RESOLVER COMPRISING A STATOR PART AND A ROTOR PART, TWO MUTUALLY ORTHOGONALLY ORIENTED PRIMARY WINDINGS ON ONE OF SAID PARTS, A SECONDARY WINDING ON THE OTHER OF SAID PARTS, MEANS FOR CONNECTING SAID ROTOR PART TO THE MECHANICAL OUTPUT OF SAID SECOND SERVOMOTOR MEANS, MEANS FOR CONNECTING ONE OF THE SECONDARY WINDINGS OF SAID SECOND TRANSMITTING RESOLVER TO ONE OF THE PRIMARY WINDINGS OF SAID SECOND COMPARISON RESOLVER, MEANS FOR CONNECTING THE OTHER SECONDARY WINDING OF SAID SECOND TRANSMITTING RESOLVER TO THE OTHER PRIMARY WINDING OF SAID SECOND COMPARISON RESOLVER WHEREBY THE SECONDARY WINDING OF SAID SECOND COMPARISON RESOLVER TRANSMITS A VOLTAGE PROPORTIONAL TO SIN (XV-C), XV BEING THE ELEVATION ANGLE OF SAID WEAPON WITH RESPECT TO SAID GIVEN PLANE, SAID VOLTAGE CONSTITUTING A PRIMARY ELEVATION CONTROL SIGNAL; COMPUTER MEANS INCLUDING SIGNAL INPUTS CONNECTED TO AT LEAST ONE OF THE SECONDARY WINDINGS OF SAID FIRST TRANSMITTING RESOLVER AND AT LEAST ONE OF THE SECONDARY WINDINGS OF SAID SECOND TRANSMITTING RESOLVER, A FIRST SIGNAL OUTPUT FOR TRANSMITTING DEFLECTION TRAVERSE CONTROL SIGNAL WHICH IS TRIGONOMETRICALLY RELATED TO THE TRAVERSE ANGLE OF SAID SIGHT AND A SECOND SIGNAL OUTPUT FOR TRANSMITTING A DEFLECTION ELEVATION CONTROL SIGNAL WHICH IS TRIGONOMETRICALLY RELATED TO THE ELEVATION ANGLE OF SAID SIGHT; MEANS FOR FEEDING THE SUM OF SAID PRIMARY AND DEFLECTION TRAVERSE CONTROL SIGNALS TO THE TRAVERSE CONTROL SIGNAL INPUT OF SAID FIRST SERVOMOTOR MEANS; AND MEANS FOR FEEDING THE SUM OF SAID PRIMARY AND DEFLECTION ELEVATION CONTROL SIGNALS TO THE ELEVATION CONTROL SIGNAL INPUT OF SAID SECOND SERVOMOTOR MEANS. 